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| author | Kazuhiko Sakaguchi | 2020-11-07 00:51:34 +0900 |
|---|---|---|
| committer | GitHub | 2020-11-07 00:51:34 +0900 |
| commit | e1f1d3c5e778f9e427e46b9bca2e12719085a6ef (patch) | |
| tree | 0c288090d2187151538e225e591bfea8c1752e97 | |
| parent | 26a35314966a28880888eefe62ef053f0b9f038f (diff) | |
| parent | aad2327376b2f76950be51a6bf22b32b0a01b2eb (diff) | |
Merge pull request #626 from CohenCyril/inj_card_bij
Generalizing inj_card_onto and inj_card_bij.
| -rw-r--r-- | CHANGELOG_UNRELEASED.md | 3 | ||||
| -rw-r--r-- | mathcomp/ssreflect/fintype.v | 4 |
2 files changed, 6 insertions, 1 deletions
diff --git a/CHANGELOG_UNRELEASED.md b/CHANGELOG_UNRELEASED.md index 81f1d27..57e5e28 100644 --- a/CHANGELOG_UNRELEASED.md +++ b/CHANGELOG_UNRELEASED.md @@ -321,6 +321,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/). + `>=< y` stands for `[pred x | x >=< y]` - in `ssrint.v`, generalized `mulpz` for any `ringType`. +- In `fintype.v`, lemmas `inj_card_onto` and `inj_card_bij` take a + weaker hypothesis (i.e. `#|T| >= #|T'|` instead of `#|T| = #|T'|` + thanks to `leq_card` under injectivity assumption). ### Renamed diff --git a/mathcomp/ssreflect/fintype.v b/mathcomp/ssreflect/fintype.v index 422d760..91d5c80 100644 --- a/mathcomp/ssreflect/fintype.v +++ b/mathcomp/ssreflect/fintype.v @@ -1300,7 +1300,9 @@ Qed. Lemma leq_card : #|T| <= #|T'|. Proof. exact: (leq_card_in (in2W _)). Qed. -Hypothesis card_range : #|T| = #|T'|. +Hypothesis card_range : #|T| >= #|T'|. + +Let eq_card : #|T| = #|T'|. Proof. by apply/eqP; rewrite eqn_leq leq_card. Qed. Lemma inj_card_onto y : y \in codom f. Proof. by move: y; apply/subset_cardP; rewrite ?card_codom ?subset_predT. Qed. |